In accordance with a rapid spread of information relevant apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the automobile industry. A lithium battery has been presently noticed from the viewpoint of a high energy density among various kinds of batteries.
Liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the improvement in structure and material for preventing the short circuit are necessary therefor. On the contrary, a lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery.
In the field of such an all solid state battery, the intention of improving the performance of the all solid state battery has been conventionally attempted while noticing an interface between a cathode active material and a solid electrolyte material. For example, in Patent Literature 1, the all solid state battery such that a reaction inhibition unit having a polyanion structure (such as borate and silicate) including a central element (such as B and Si) with an electronegativity of 1.74 or more, which covalently bonds to plural oxygen elements, is formed at the interface between a cathode active material and a solid electrolyte material is disclosed. This is such that the formation of the reaction inhibition unit having a polyanion structure with high electrochemical stability at the interface between a cathode active material and a solid electrolyte material inhibits interface resistance between a cathode active material and a solid electrolyte material from increasing with time to intend higher durability of the battery.
On the other hand, in Patent Literature 2, it is disclosed that the cathode active material surface of an all solid lithium battery is coated with a lithium ion conductive oxide to inhibit a high resistance layer from being formed at an interface between the cathode active material and a sulfide solid electrolyte.